The invention relates to a ceramic electrostatic chuck (ESC) useful in the manufacture of semiconductor devices.
Electrostatic chucks are used to hold semiconductor wafers and other substrates in place in various types of processing equipment including plasma processing equipment. Electrostatic chucks typically include one or more conductive electrodes underlying a dielectric (insulating) or semi-conductive ceramic layer across which an electrostatic clamping field can be developed. Unlike mechanical clamping devices, electrostatic chucks allow an entire surface of the substrate to be exposed to the plasma. Additionally, the electrostatic chuck clamps the substrate more uniformly to the baseplate to allow a greater degree of control of the wafer temperature.
Various electrode patterns are known for use with electrostatic chucks. With mono-polar electrodes, the electrode is typically in the form of a flat plate. With bipolar electrodes, the separate electrodes have been arranged as half disks or as an inner disk and an outer annulus. Examples of bipolar chucks of this type are disclosed in Tomaru et al. (U.S. Pat. No. 6,071,630) and Logan et al. (U.S. Pat. No. 5,055,964). Electrode patterns have also been proposed where the electrodes are arranged in comb patterns. See, for example, Barnes et al. (U.S. Pat. No. 5,207,437). Other patterns are disclosed in Shufflebotham et al. (U.S. Pat. No. 5,838,529) and Logan et al. (U.S. Pat. No. 5,155,652).
Electrostatic chucking devices which utilize ceramic materials are disclosed in U.S. Pat. Nos. 5,151,845; 5,191,506; 5,671,116; 5,886,863; 5,986,874; 6,028,762; 6,071,630; 6,101,969; and 6,122,159. Ceramic ESCs are typically made using multi-layer ceramic packaging technology. Multi-layer ceramic packaging technology involves printing refractory metal patterns on ceramic green sheets, assembling the sheets into laminates and co-firing the resulting assemblies. See, for example, U.S. Pat. Nos. 4,677,254; 4,920,640; 5,932,326; 5,958,813; and 6,074,893. Various metallizing compositions for use with ceramic substrates are disclosed in U.S. Pat. Nos. 4,381,198; 4,799,958; 4,806,160; 4,835,039; 4,861,641; 4,894,273; 4,940,849; 5,292,552; 5,932,326 and 5,969,934.
Since the sintering of ceramic ESCs is normally conducted at very high temperatures, differences in the coefficient of thermal expansion between the electrode material and the ceramic material can cause the build-up of internal stresses in the chuck. These internal stresses can lead to warping or, in some cases, actual damage to the ceramic ESC. Accordingly, there is a need in the art for overcoming warping and other problems associated with the build-up of internal stresses during manufacture of ceramic ESCs.
Also, since the radio frequency (RF) power used to generate the plasma and to bias the substrate is typically applied to a separate electrode underlying the ESC clamping electrode, it would be desirable in such cases to maximize the RF transparency of the clamping electrode.
In a first embodiment of the invention, a sintered ceramic electrostatic chucking device is provided. The chucking device includes an electrostatic clamping electrode embedded in a joint-free monolithic sintered ceramic body. The clamping electrode includes at least one pattern of a substantially planar electrically conductive material wherein the maximum straight line length in the electrode pattern is 1.0 inch. In a preferred embodiment of the invention, the maximum straight line length in the electrode pattern is 0.25 inches. The electrode pattern can comprise a single electrically conductive pattern or at least two electrically isolated patterns of conductive material.
A method of making the sintered ceramic electrostatic chucking device set forth above is also provided. The method comprises steps of: providing a first layer comprising a ceramic material in a green state; forming a pattern of at least one strip of an electrically conductive material on a first major surface of the first layer; providing a second layer comprising ceramic material in green state; assembling the second layer on the first major surface of the first layer; and cofiring the first and second layers to form a monolithic joint-free sintered ceramic body with an embedded electrode layer. Due to the characteristics of the electrode pattern employed, the sintered electrode layer remains substantially planar after firing. In a preferred embodiment of the method set forth above, the forming step comprises forming a pattern from a paste comprising particles of an electrically conductive material and the cofiring step comprises sintering the particles of the electrically conductive material to form a sintered clamping electrode.
A method of treating a substrate in a process chamber including the aforementioned electrostatic chucking device is also provided. The method comprises steps of: electrostatically clamping the substrate to the electrostatic chucking device and processing the substrate. The method can also include steps of coupling RF energy of at least one frequency through the electrostatic chucking device to generate a plasma adjacent the exposed surface of the substrate and processing the substrate with the plasma.
In a second embodiment of the present invention, an electrostatic chucking device useful for supporting semiconductor substrates in a semiconductor processing chamber is provided. The chucking device includes a body of electrically insulating or semi-conductive material having a support surface on which a semiconductor substrate can be electrostatically clamped and a clamping electrode adapted to electrostatically clamp the substrate to the support surface. The chucking device also includes a lower electrode adapted to couple radio frequency energy through the clamping electrode and into an open space in the vicinity of a substrate clamped to the support surface. In a first embodiment of this electrostatic chucking device, the clamping electrode has a resistivity such that the clamping electrode is highly transparent to the coupling of radio frequency energy into the plasma chamber. In a second embodiment of this electrostatic chucking device, a substantially uniform distribution of radio frequency energy develops across the lower electrode when radio frequency power is applied thereto and the clamping electrode has a sufficiently high lateral radio frequency impedance in a direction parallel to the support surface such that radio frequency power coupled through the clamping electrode and into the plasma chamber is substantially uniformly distributed across the substrate support surface.
A method of treating a semiconductor substrate in a process chamber including an electrostatic chucking device as set forth above is also provided. The method includes steps of electrostatically clamping the substrate to the electrostatic chucking device and coupling RF energy of at least one frequency through the electrostatic chucking device.